Additive manufacturing is a revolutionary technology, that is distinct from traditional subtractive machining techniques, which rely on the removal of material by methods such as cutting or drilling, and generally includes the techniques of rapid prototyping (RP) and rapid manufacturing (RM).
Generally, a recent additive manufacturing process involves the use of a high power laser, such as selective lase sintering/melting (SLS/SLM), using which a laser beam is used for selectively fuses powdered material by scanning cross-sections generated from a 3-D digital description of a part on the surface of a powder bed, and after each cross-section is scanned, the powder bed is lowered by one layer thickness for allowing a new layer of material to be applied on top and then enabling the process to repeat until the 3D part is completed. Comparing to conventional machining processes, the SLS/SLM technology is in wide use around the world due to its ability to easily make very complex geometries directly from digital CAD data, such as parts with complex internal flow passages and internal structures.
Please refer to FIG. 1, which is a schematic view of a conventional additive manufacturing process. As shown in FIG. 1, a conventional additive manufacturing process is performed by projecting a laser beam 1 emitted either from a continuous wave (CW) laser source or a long pulse laser source on a powder 2 so as to melt or sinter the powder 2. However, since the surface reflective index of the powder 2 can be higher than 90%, the laser beam 1 is generally being scattered outside the designed scan area 3, causing poor molding accuracy due to severe heat diffusion.